"Prawn" is most commonly used to describe a species of shellfish that is part of the lobster family. These prawns have minuscule (very small) claws and bodies shaped like tiny Maine lobsters. Their meat has a sweet delicate flavor. They are 6 to 8 inches (15 to 20 centimeters) long and have pale-red bodies deepening to dark-red tails. Included in this definition of "prawn" are Dublin bay prawn, Danish lobster, Italian scampi, langostino (Spanish), langoustine (French), Caribbean lobsterette, and Florida lobsterette.

"Freshwater" prawns are prawns that migrate from saltwater to freshwater to spawn (lay eggs). They look like a cross between a shrimp and a lobster. Their abdomens are narrower and legs are longer than those of shrimp.

The term "prawn" is also loosely used to describe any large shrimp, especially one that weighs at least one-fifteenth of a pound (0.45 kilograms).